Scaling Diamond Raman Lasers and Beam Combiners into the Kilowatt, Thermally Affected, Regime

In this project, the research team investigated the use of diamond as a nonlinear optical material for Raman beam conversion. They studied the thermal limits for power scaling in detail using a novel laser-probe diagnostic, based on second-order Raman scattering to observe the phonon decay dynamics. This enabled an enhanced understanding of thermal effects and power limits in diamond and improved models for kilowatt diamond converters and lasers. The project increased diamond Raman laser powers to the kilowatt level and thermally-affected regime. A maximum power of 1.2kW was demonstrated for pulses of 100 microseconds, a duration sufficiently long to establish quasi-steady-state thermodynamic conditions in the diamond bulk. The first evidence for thermal effects was detected through analysis of the output beam divergence, although no major deterioration in efficiency or beam quality was observed. The results highlight potential for realizing continuous kilowatt-class TEM00 lasers and amplifiers using single diamond elements at room temperature.